bash: fix `bashrcExtra` interactive shell test
bash: fix `bashrcExtra` interactive shell test

To determine if bash is running interactively test whether "$-"
contains "i".

See: https://www.gnu.org/software/bash/manual/html_node/Is-this-Shell-Interactive_003f.html

rycee/home-manager,rycee/home-manager,rycee/home-manager